Picatinny are close to Weaver, but they are not the same. Same general style, but not the same specifications.
The Picatinny is wider than the Weaver and the claw angle is different. And the depth and width of the cross slots are different, too.
It is best to use Picatinny rings with Picatinny rails, and Weaver rings with Weaver raisl, though you can get away with mixing them up fairly well.
For any type of precision use, mixing the two will not give optimum results, especially is using a quick release style of ring.